|
Home »
Rocks and Minerals » Metamorphic Rocks
Metamorphic Rocks
Pictures of Foliated and Non-Foliated Rock Types
Metamorphic rocks have been modified by heat, pressure and chemical process usually while buried deep below Earth's surface.
Exposure to these extreme conditions has altered the mineralogy, texture and chemical composition of the rocks. There are two basic types of metamorphic rocks: 1) foliated metamorphic rocks such as gneiss, phyllite, schist and slate which have a layered or banded appearance that is produced by exposure to heat and directed pressure; and, 2) non-foliated metamorphic rocks such as marble and quartzite which do not have a layered or banded appearance. Pictures and brief descriptions of some common types of metamorphic rocks are provided below.
Amphibolite
|
 |
|
Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. It is composed primarily of amphibole and plagioclase, usually with very little quartz. The specimen shown above is about two inches (five centimeters) across.
|
Return to Top
Gneiss
|
 |
|
Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals. The specimen shown above is about two inches (five centimeters) across.
|
Return to Top
Hornfels
|
 |
|
Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was "baked" while near a heat source such as a magma chamber, sill or dike. The specimen shown above is about two inches (five centimeters) across.
|
Return to Top
Marble
|
 |
|
Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate. The specimen shown above is about two inches (five centimeters) across.
|
Return to Top
Phyllite
|
 |
|
Phyllite is a foliate metamorphic rock that is made up mainly of very fine-grained mica. The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate in grade between slate and schist. The specimen shown above is about two inches (five centimeters across).
|
Return to Top
Quartzite
|
 |
|
Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz. The specimen above is about two inches (five centimeters) across.
|
Return to Top
Schist (Chlorite Schist)
|
 |
|
Schist is metamorphic rock with well developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss. The specimen shown above is a "chlorite schist" because it contains a significant amount of chlorite. It is about two inches (five centimeters) across.
|
Return to Top
Schist (Garnet Schist)
|
 |
|
Schist is metamorphic rock with well developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss. The specimen shown above is a "garnet schist" because it contains a significant amount of garnet. The small crystals visible in the rock are small red garnets. It is about two inches (five centimeters) across.
|
Return to Top
Schist (Muscovite Schist)
|
 |
|
Schist is metamorphic rock with well developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss. The specimen shown above is a "muscovite schist" because it contains a significant amount of muscovite mica. It is about two inches (five centimeters) across.
|
Return to Top
Slate
|
 |
|
Slate is a foliated metamorphic rock that is formed through the metamorphism of shale. It is a low grade metamorphic rock that splits into thin pieces. The specimen shown above is about two inches (five centimeters) across.
|
Return to Top
|
The rock photos above were taken by Ann Bryant and are copyright by Geology.com. |
|
 |
|
Sliding Rocks: How these rocks slide across a dry lake bed is a mystery. Learn what is thought to move them. © iStock / S. Hoerold
|
|
Herkimer Diamonds: Learn how to find these doubly terminated quartz crystals at Herkimer, NY. |
|
"A Grain of Sand": A gallery of sand grains from around the world as photographed through a microscope by Dr. Gary Greenberg. |
| Meteorites: Learn about meteorites and how to identify them. |
|
The Many Uses of Gold: Learn how the unique properties of gold make it extremely suited for a large number of industrial uses. |
|
Uses of Granite: The rock used for everything from kitchen counters to street curbing to the facing stone of skyscrapers. |
|
|
